CN101953060B - Distributed Electric Energy Harvesting System Using DC Power - Google Patents

Abstract

A system and method for integrating DC power. Each power supply is coupled to a converter. Each converter will convert input power to output power by monitoring and maintaining a maximum current value. In fact, all the input power is converted to output power by the conversion device output voltage variation. The individual conversion devices are connected in series with one another. The other inverter is connected in parallel with the series-connected converter device, and converts the current input into the inverter from the converter into alternating current output. The inverter can control the current voltage input into the inverter by varying the amount of series current output by the converter. The series current and the output power of the inverter switch determine the output voltage of each inverter.

Description

Distributed Electric Energy Harvesting System Using DC Power

Related Application Cross Reference

This application claims priority over the following U.S. provisional patent applications entitled "Monitoring, Management, and Maintenance of Distributed Solar Distributed Power Harvesting System for Power Sources" (Serial No. 60/868,893, submitted on December 6, 2006), entitled "System, Method and Device for Chemical Independent Battery Control" (Serial No. 60/868,962, submitted on December 7, 2006) , titled "Distributed Power Source Electric Energy Harvesting System and Method" (Serial No. 60/908,095, March 26, 2007), titled "Harvesting Electric Energy from DC Power Sources" (Serial No. 60/916,815, submitted on May 9, 2007) . The entire contents of the aforementioned patents are incorporated by reference into this patent application. Moreover, this patent application and common U.S. patent application No. 11/950,224, filed on December 4, 2007, entitled "Current Bypass of Distributed Electric Energy Harvesting System Using DC Power Supply", patent application No. 11/950,271, 2007 The patent application serial number 11/950,307 filed on December 4, 2007 entitled "Using Direct Current Distributed Electric Energy Collection System", and the title "Using Direct Current Distributed Electric Energy Collection System" submitted on December 4, 2007, these The entire content of the patent application is also incorporated into this application by reference.

technical field

The field of the invention relates generally to distributed DC power generation, and more particularly to the management of distributed DC power sources installed in series.

Background technique

Recently, increasing interest in renewable energy has led to increased research on distributed energy generation systems, such as photovoltaic cells (PV), fuel cells, chemical cells (e.g., batteries for hybrid electric vehicles), etc. Various topological theories have been proposed to connect these power supplies to loads, taking into account various parameters such as voltage/current conditions, operating conditions, reliability, safety, cost, etc. For example, the output voltage of most such power supplies is relatively low (typically a few volts for a single battery or tens of volts for batteries connected in series), so many of these batteries need to be connected in series to achieve the required operating voltage. On the contrary, series connection cannot provide the required current, so several groups of batteries connected in series need to be connected in parallel to provide the required current.

In addition, it is well known that power generation from these sources depends on production, operational and environmental conditions. For example, various conflicts in the production process may cause two identical power supplies to have different power output characteristics. Similarly, two identical power supplies may react differently to operating and/environmental conditions such as load, temperature, etc. In actual assembly, different power sources may also encounter different environmental conditions. For example, some sail panels of a solar device may be exposed to the entire sunlight, while others may be blocked, so the output power is different. In a multi-battery device, some of the batteries may age to different degrees, thus resulting in different output power. While these issues and the solutions provided by the present invention apply to distributed power systems, the following discussion turns to solar energy for better understanding through specific examples.

The arrangement of a conventional solar power generation system 10 is shown in FIG. 1 . Since the voltage provided by each solar panel 101 is relatively low, several panels are connected in series to form a string of panels 103 . For large devices, when higher current is required, several strings 103 can be connected in parallel to form a complete system 10 . The solar panels are installed outdoors, and they are wired into a maximum power point tracking (MPPT) module 107 and an inverter 104 . MPPT 107 is generally used as a component of inverter 104 . The electrical energy collected from the DC power supply is sent to the inverter 104, which converts the fluctuating direct current (DC) power into alternating current (AC) power of a certain voltage and frequency, usually 110V or 220V, 60Hz or 220V, 50Hz (interesting Yes, many inverters in the US first generate 220V, which is then split into two 110V output ports in the distribution box). The AC power output by the inverter 104 may then be used to run electrical equipment or input into the power supply network. In addition, the device can also be disconnected from the grid, and the power output from the inverter can be directly input to the conversion and charging/discharging circuit to store excess power, such as charging a battery. If it is connected to a battery, the inverter stage can be ignored, and the direct current output from the MPPT stage 107 can be directly supplied to the charging/discharging circuit.

As mentioned above, the voltage and current provided by each solar panel 101 are very low. The problem facing solar cell designers is how to combine these low-voltage solar sources to generate standard AC power at 120V or 220V root square (RMS). Achieving high power from a low-voltage power supply requires very high current, and the power calculated as the square of the current (I ² ) will have a large conduction loss. Furthermore, a power inverter, such as the inverter 104 used to convert direct current to alternating current, is most efficient when its input voltage is slightly higher than its output RMS voltage multiplied by its square root. Therefore, in many practical applications, power sources such as the solar panel 101 are usually connected together in order to achieve the correct voltage or current. The most common approach is to connect these supplies in series to achieve the desired voltage, and then in parallel to achieve the desired current, as shown in Figure 1. A large number of solar panels 101 are connected together to form series panels 103 , and then these series panels 103 are connected in parallel with power inverters 104 . The solar panels 101 are connected in series in order to achieve the minimum voltage required by the inverter. Multiple strings 103 are then connected in parallel to provide greater current, thus having higher output power.

However, this configuration is advantageous in terms of cost and simple structure, but there are some defects in this structure reported in literature. One of the known drawbacks is that the non-optimized power harvested from the individual solar panels can lead to the inefficiencies mentioned below. As mentioned earlier, the output of a DC power supply is affected by many conditions. Therefore, in order to maximize the output power of each power supply, a device is required to consider voltage and current at the same time, and can output the maximum power under the prevailing conditions at present. As conditions change, the voltage and current output should also need to change simultaneously.

FIG. 2 shows a series connection of DC power sources, such as solar panels 201 a - 201 d , connected to MPPT circuit 207 and inverter 204 . Plotted current versus voltage (IV) characteristics ( 201 a - 210 d ) are located to the left of each DC power supply 201 . For each DC power supply 201, the current decreases as the output voltage increases. Under certain voltage value conditions, the current becomes zero. Some applications may assume that it is a negative value, which means that the power source becomes a receiver at this time. Bypass diodes are used to prevent the power supply from becoming a sink. Bypass diodes are used to prevent the power supply from becoming a sink. The output power of each power supply 201 is equal to the product of current and voltage (P=I*V), and varies with the voltage obtained from the power supply. Under certain current and voltage conditions, when the current value is close to zero, the output power is the maximum. Ideally, the generating battery is operating at its maximum power. The purpose of MPPT is to find the maximum power point, and then make the system work under the condition of this point to maximize the power obtained from the power supply.

In conventional typical solar cell arrays, different algorithms and techniques are used to optimize the integrated power output of the system 10 using the MPPT module 107 . The MPPT module 107 receives the current in each solar panel, gathers it together and tracks the maximum power point under this current condition to provide the maximum average power. This way the average voltage you get from these sails starts to drop if you get more current, so less power is collected. The MPPT module 107 is used to maintain the maximum average power output current of the entire system 10 .

The maximum power point tracking technology was published by T.Esram and P.L.Chapman in IEEE Energy Conversion Transactions "Comparison of Several Photoelectric Array Maximum Power Point Tracking Technologies" (accepted to be published, 2006 PP Volume 99, No. 1- 1-page digital designation 10.1109/TEC.2006.874230), the entire contents of which are incorporated into this application by reference.

However, since the power supplies 201a-201d are connected in series to a single MPPT 207, the MPPT must select a single point, which may be the MPP average of the series supplies. In fact, it is quite possible that the MPPT's operation at the I-V point is optimal with only a few power supplies or none at all. In the example shown in Fig. 2, the selected point is the maximum power point of the power supply 201b, but it deviates from the maximum power points of the power supplies 201a, 201c and 201d. As a result, this layout cannot work at the maximum achievable efficiency.

Returning to the example of the solar energy system 10 shown in FIG. 1, maintaining a predetermined constant output voltage of the series sails 103 would result in a lower solar power output than would otherwise be possible. Moreover, the current carried by each row of sail panels in series will pass through all the solar panels along the string of sail panels. If solar panels are mismatched due to manufacturing differences, aging or if they malfunction or are placed under different shade conditions, the current, voltage and power output by each panel will be different. Since passing a single current through all sailboards connected in series can cause each board to operate at a non-optimal power point, and can also cause mismatched boards to create "hot spots" due to high current flow. Because of the drawbacks of this and that of traditional harvesting methods, solar panels need to be properly matched. In some cases, external diodes are provided to bypass badly mismatched solar panels. In the traditional multi-tandem configuration, all series-connected sailboard groups must be composed of absolutely the same number of sailboards, and the sailboards must be selected in the same model and in the same spatial direction so that they are always exposed to the same sunlight conditions. This approach is difficult and expensive to implement.

Various topological methods have been proposed to overcome the above-mentioned deficiencies of the tandem solar device. For example, some have proposed coupling inverters to each DC source and then paralleling these inverters. Others propose connecting the DC/DC converters to the DC source and then connecting all the converters in series or in parallel to a central inverter. Among the DC/DC converters proposed for use with DC power supplies are boost converters, buck converters, buck-boost converters or Cuk converters. It has also been proposed to integrate the MPPT on each DC power source, for example, to each solar panel and in series with the panel.

For further discussion of the above issues related to distributed power generation and solar panels, the reader is strongly encouraged to review the following literature, which may or may not be the preferred process.

- Cascaded DC-DC Converter Converter Connections for Optoelectronic Modules, G.R. Walker and P.C. Sernia, Power Electronics Experts Conference, 2002 (PESC02), IEEE Vol. 1, Cairns, Australia, pp. 24-29.

- Topological approach to decentralized solar inverters using low voltage AC-bus, Bjorn Lindgren.

- Integrated Optoelectronic Maximum Power Point Tracking Converters, Johan H.R. Enslin et al., IEEE Transactions on Industrial Electronics, Vol. 44, No. 6, December 1997.

- A New Interface for Photovoltaic Fanboard Distributed Converters, R.Alonso et al., 20th European Photovoltaic Solar Energy Congress, June 6-10, 2005, Barcelona, Spain.

- Smart Photovoltaic Modules for Grid-Connected Photovoltaic Systems, Eduardo Roman et al., IEEE Transactions on Industrial Electronics, Vol. 53, No. 4, August 2006. Also in Spanish patent application ES2249147.

- Modular Fuel Cells - High Performance and Reliability Enhanced Modular DC-DC Converter Concept, L.Palma and P.Enjeti, Power Electronics Experts Conference, 2007, PESC2007, IEEE Volume, Journal, 17-21 June 2007 Pages 2633-2638. Digital ID 10.1109/PESC.2007.4342432.

- Experimental Results of Smart Photovoltaic Modules for Grid Connected Photovoltaic Systems, R.Alonso et al., Proceedings of the 21st European Photovoltaic and Solar Energy Congress, Dresden, Germany, September 4-8, 2006.

- Optoelectronic Module Cascaded DC-DC Converter Connections, G.R. Walker and P.C. Sernia, IEEE Transactions on Power Electronics, Vol. 19, No. 4, July 2004.

- Cost Efficiency of Shading Tolerant Photovoltaic Systems, Quaschning, V.; Piske, R.; Hanitsch, R., Euronsun96, Friburg, 16-19 September 1996.

- Evaluation test results of new distributed MPPT converters, R.Orduz and M.A.Egido, 22nd European Photovoltaic Solar Energy Congress, September 3-7, 2007, Milan, Italy.

-Energy Integrated Management System for Photovoltaic Applications, S.Uriarte et al., 20th European Photovoltaic Solar Energy Conference, June 6-10, 2005, Barcelona, Spain.

- US published patent 2006/0185727.

As with some of the processes described above, integrating inverters onto individual battery cells has many disadvantages, including high cost, safety (especially for solar installations), and low reliability. Therefore, series connection is preferred, especially for solar panel installations. The proposal of including the DC-DC converter and MPPT in a single battery cell and then outputting in series to the inverter is very attractive. However, integrating the MPPTs into individual sailboards is also problematic in tandem applications, since each MPPT is trying to start its power supply at a different current, while the same current must flow through all the sailboards in the tandem. Also, it is unclear which type of DC-DC converter will provide the best results and how to incorporate MPPT into this arrangement. Therefore, there is also a need for effective topological solutions to connect multiple DC power sources to loads, such as grids, batteries, and the like.

As already mentioned, various environmental and operating conditions affect the output power of a DC power supply. Factors such as solar panels, solar radiation, ambient temperature, and shading from nearby objects such as trees or distant objects such as clouds all affect the power output of each solar panel. The output power depends on the number and type of sails used, and the power output of each solar panel may have a large difference in voltage and current. It can be difficult for homeowners, and even professional installers, to verify that a solar system is functioning properly. Many other factors, such as aging, dust and dirt deposits, and degradation of module functionality, can affect the performance of solar panels over time.

The sensitivity of photovoltaic sailboards to external conditions is excellent, especially when using concentrated photovoltaic systems (CPV). With this type of device, solar radiation is concentrated by prisms or mirrors onto small battery cells. These battery cells are much more efficient than ordinary photovoltaic cells. They use a technology called duplex or triplet, in which a large number of p-n connections are formed on top of each other. The connection points convert certain wavelengths of light into electrical energy, and other wavelengths of light Allows to be transformed through to the next join point. Therefore, these cells appear to be more efficient (up to 40% efficiency). Since these cells are relatively expensive, they are typically used in CPV applications where smaller cells are required. Nevertheless, the output power of CPV devices now depends on several factors: fluctuations in the intensity of sunlight in different wavelength bands (not just the total intensity), defects or deformation of the prisms or mirrors used, etc. Thus, a single MPPT in a multi-sail setup would result in a large loss of power, whereas using an MPPT at the sail (or battery) level as described in the present invention would be of great advantage.

Another area where traditional photovoltaic installations face more problems is the development of the building integrated photovoltaic (BIPV) market. In BIPV installations, the panels are installed during the construction of the building – either as roof panels or as structural or additional components such as walls and windows. Consequently, the BIPV installation will be partially shaded to a large extent locally due to the presence of other structural elements in the vicinity of the sail. Also, the panels are naturally fixed to different sides of the building, so the lighting conditions each panel receives can vary greatly. Since the traditional solution is to string the sailboards together and then connect to the node MPPT, this will cause a lot of power loss. Solutions that can harvest more power are clearly a big improvement on this type of device.

However, another problem with conventional installations is that energy efficiency is low when sunlight is low. Most inverters require a certain minimum voltage (typically 150V to 350V) in order to start running. If the light is insufficient, the accumulated voltage formed by the sailboard cannot reach the minimum value, and the power is lost. A solution that boosts the voltage during low light conditions would thus allow the energy generated to be harvested.

In the process of installing solar panels according to the traditional configuration 10, installers can check the current and voltage of each panel, each row of panels and the entire array of panels by testing equipment to determine the correctness of the installation and the performance of the panel array. In practice, however, individual panels and tandem rows of panels generally cannot be tested at all or only before they are connected. This is because the current method of measurement is either by connecting in series to the solar panel array or by using a resistor on the array, which is obviously inconvenient. Instead, pass/fail testing is done only on the entire unit at the next higher level.

After initial testing of the device, the solar array is connected to the inverter 104, optionally including a monitoring module to monitor the performance of the entire array. The performance information gathered from inverter 104 monitoring includes the total output power and generation efficiency of the array, but this information lacks detailed information about the operation of individual solar panels. Thus, the performance information provided by the inverter 104 monitoring function is often insufficient to understand whether power loss is due to environmental conditions, solar array malfunctions, or poor installation or maintenance. Also, the combined information does not indicate which of the solar panels 101 is the cause of the detected power loss.

In view of the above, a new proposed topology for connecting multiple DC sources to the load should lend itself to easy testing and health verification during and after installation.

Contents of the invention

The following is a summary of the present invention, in order to let everyone have a basic understanding of some aspects and characteristics of the present invention. This summary is not an overview of the invention, nor is it intended to identify key or critical elements of the invention or to delineate the scope of the invention. Its sole purpose is to present some concepts of the invention in a simple and clear manner as a prelude to the more detailed description that is presented later.

The content of the present invention provides a topological method for connecting distributed DC power sources in series to a central power supply device, such as a single inverter or a single converter. The content of the present invention describes a system and method capable of monitoring a single DC power source in a distributed power collection device and adjusting the current and voltage of each DC power source to maximize the transmission power of each DC power source.

According to various contents of the present invention, the distributed electricity collection system is composed of the following parts: several DC power sources; several converters, and each converter is composed of several parts: connected to the input terminals of each DC power source, connected in series The output terminal of the converter, thereby forming a row of series connection; the circuit for setting the voltage and current at the input terminal of the converter according to a predetermined standard; and the power conversion part that converts the power received at the input terminal into the output power of the output terminal; coupled to the row series connection A power supply device for sailboards, the power supply device is composed of control components that maintain a predetermined value of electricity input to it. The control unit may maintain a predetermined value voltage input to the power supply. The control unit may maintain a predetermined value of current delivered to the power supply. The power supply unit consists of a direct current/alternating current (DC/AC) inverter. The power supply device may include a battery charger. The circuit may contain MPPT components that set the voltage and current at the inverter input to maximize the power of each DC source. The power conversion section includes: a buck converter, a boost converter, a controller that selectively activates the buck converter or the boost converter according to the MPPT components and the output terminal voltage and current. The buck converter and boost converter can share an inductor, and the controller includes a pulse-width regulation section. The control section may include a bypass regulator connected in parallel with the power supply device for regulating the input voltage to maintain a predetermined input voltage. The system may further comprise one or more additional sailboard strings coupled to the power supply. The system may also include: several current sensors and several voltage sensors; wherein each current sensor and each voltage sensor are coupled between the respective converter and the DC power supply, and input current information and voltage information to the MPPT component. Each of the several DC power sources may contain a solar panel or a building-integrated solar panel. At least one of these DC power sources may contain a fuel cell. At least one of these DC power sources may contain a battery. Each converter can also include a safety module, which is used to limit the output power to a predetermined safe value until a predetermined event changes. Predetermined events can include a load exceeding a predetermined limit, which can be used to detect converter status or discharge signals. Each converter may also comprise several switching means, each switching means constituting a current bypass of at least one DC power supply. A solar panel may comprise several strings of battery cells, each string comprising solar cells connected in series and switching means coupled to a shunt of the solar cells connected in series. These switching devices may comprise a transistor. Each converter may also include a monitoring module, which is used to monitor and transmit state-related data. The state-related data includes at least one of the following information: current input to the converter, voltage input to the converter, temperature of the power supply, temperature of the input converter Power and existing lighting levels.

According to various aspects of the present invention, there is provided a method for harvesting electrical energy from a distributed power system comprising several DC power sources and several DC converters, the method consisting of the following aspects: coupling each power source to on the respective DC converters; connect the power converters in series, at least one series group; couple the series groups to the power transmission device; set the current and voltage input into the power transmission device at predetermined values, so that the The current of the group changes with the power of the power supply; the output power of each power supply is controlled separately, and the voltage and current input to the respective converters are respectively changed according to the preset standard. Fixing an input voltage or input current may include setting to a predetermined constant value. Coupling the series group to the power transmission device It is possible to connect the series group to the DC/AC inverter and fix the input voltage to the inverter. Power output monitoring may include tracking the maximum power level of the power supply. Varying the input voltage and current separately involves setting the input voltage and current to draw the maximum amount of power from each power source. The method may also include converting the input voltage and current of each converter individually to an output power in terms of amperage and floating volts, the amperage being indicated by the current flowing through the series group. The method may also include separately monitoring the load of each converter, limiting the output power of each converter to keep it at a preset safe value until the load reaches the preset value. The method may also include monitoring the output power of at least one of the power supply and the DC converter, and switching current to the bypass when the output power exhibits predetermined characteristics. The method may also include operating each power converter individually to monitor and report power related data. Power-related data includes at least one of the following information: current delivered to the converter, voltage delivered to the converter, power supply temperature, power delivered to the converter, and existing illuminance.

According to various aspects of the present invention, a solar power generation device is described, which is composed of the following components: a DC/AC inverter, including an input voltage or current device to maintain a predetermined value; The AC inverters are connected in parallel, and each series group contains: several solar panels and several inverters. Each inverter consists of: coupled to the input of the respective solar panel, connected in series to the output of other inverters, thereby forming a series group; MPPT components, used to set the conversion according to the maximum power point of the respective solar panel The voltage and current at the input terminal of the device; the power conversion part is used to convert the power received at the input terminal into the output power at the output terminal. The predetermined value may include a constant value. The power conversion part can convert the power at the input terminal into output power, so that the current is equivalent to the total power provided by several solar panels connected in series. These solar panels in series are divided according to the predetermined voltage at the input terminal of the inverter. The power conversion part may include a power conversion controller, which is used to control the pulse width adjustment of the power conversion part, so that the current of the output power is equivalent to the total power provided by several solar panels connected in series. The input terminal is divided by a predetermined voltage. Each power conversion section can include: a buck converter, a boost converter, a pulse width regulator; and a digital controller that controls the pulse width regulator to selectively activate the buck converter or boost converter. Each series group can also include: several current sensors, which are used to measure each output current of a single solar panel, and send the measured current signals to their respective digital controllers; several voltage sensors, which are used to The output voltage of a single solar panel is measured each time, and the measured voltage signal is sent to the respective digital controller. Here each digital control can adjust voltage and current for maximum power supply. The solar power generation device may also include a safety module, which is used to limit the output voltage to a predetermined safe value, so that the load does not exceed the predetermined limit applicable to the converter. The solar power generation device according to claim 30, wherein the solar sail comprises several battery cell groups, each battery cell group contains battery cells connected in parallel, and the switching device is coupled to form a bypass of the solar cell cells connected in series. The switching device may comprise a transistor. Each converter may also include a monitoring module for monitoring and transmitting power-related data. The power-related data includes at least one of the following: current input to the converter, voltage input to the converter, power supply temperature, spatial orientation of the power supply, and existing illuminance.

In accordance with aspects of the present invention, there is provided a method for improving the reliability of distributed power system components comprising several DC power sources coupled to a central load, the method comprising: coupling the DC power sources to a central load On the load; maintain the voltage input to the central load at a predetermined value, which is a safe operating voltage when the component is loaded; change the current input to the central load according to the amount of power obtained by the DC power supply. The central load may include a DC/AC inverter and a transmission maintenance step to maintain the input inverter voltage. Coupling the DC power source may include coupling each solar panel to a respective inverter, and coupling all inverters to an inverter. The method may also include operating each inverter to boost the voltage obtained from each solar panel whenever each solar panel begins to output electrical power.

Description of drawings

The drawings accompanying hereto constitute a part of this specification and are used to illustrate specific details of the invention and, together with the description, serve to explain and illustrate the principles of the invention. The purpose of these drawings is to illustrate the main features of example details in a diagrammatic manner. These drawings are not intended to depict every aspect of actual detail nor relative dimensions of the components drawn, as they are not drawn to scale.

Figure 1 depicts a traditional centralized power harvesting system using a DC power source.

Figure 2 depicts the current vs. voltage characteristic curve of a single series-connected DC power pack.

Fig. 3 depicts a distributed electric energy harvesting system using a DC power source according to the present invention.

Figures 4A and 4B illustrate the operation of the system shown in Figure 3 under various conditions in accordance with the various aspects of the present invention.

Figure 4C depicts an entity of the present invention where an inverter controls the output current.

Fig. 5 illustrates a distributed electric energy harvesting system using a DC power supply according to other items of the present invention.

Fig. 6 illustrates a DC-to-DC converter according to various aspects of the present invention.

Figure 7 illustrates an example of a power converter in accordance with the various aspects of the invention, including the control features of the invention.

Figure 8 illustrates the layout of solar panels according to the previous process.

Fig. 9 illustrates an example of a layout for reducing power loss of solar tandem sail panels according to the details described in the present invention.

Fig. 10 illustrates another arrangement for reducing the power loss of solar series sail panels according to the details described in the present invention.

Figure 11 illustrates a layout for bypassing solar tandem panels according to the details described in the present invention.

Detailed ways

The topology provided by the present invention solves many of the problems associated with existing topologies and has many advantages over existing topologies. For example, the invented topology allows series connection of unmatched power sources such as unmatched solar panels, panels of different models and power ratings or even panels made of different manufacturers and semiconductor materials. This topology allows series connection of power supplies that operate under different conditions, for example, solar panels under different light or temperature conditions. This topology can also be used to install panels in series on different orientations or sections of the roof or building. This and other features and advantages are apparent from the following detailed description.

Aspects of the present invention provide systems and methods for combining the power of multiple DC sources into a single source. In aspects of the invention, each DC power source is associated with a DC-DC power converter. Series connection of modules formed by connecting DC power supplies to associated converters to provide a string of modules. The modules are then connected in series to an inverter that keeps the input voltage constant. The maximum power point control loop in each converter collects the maximum power of each DC power supply, and transmits this power as the output of the power converter. For each converter, substantially all of the input power is converted to output power, and in some cases the conversion efficiency may be 90% or higher. In addition, control is performed by fixing the input current or input voltage of the converter at the maximum power point and allowing the converter output voltage to vary. For each power supply, one or more sensors monitor the input power level of the associated converter. In some aspects of the invention, the microcontroller uses pulse width modulation to adjust the duty cycle used to transfer power from the input to the output, ie maximum power point tracking and control in each converter.

One aspect of the invention provides a greater degree of fault tolerance, maintenance and durability by monitoring, recording and/or communicating the performance of individual solar panels. In one aspect of the invention, the microcontroller used to track the maximum power point can also be used to perform monitoring, recording and communication functions. These features allow for quick and easy troubleshooting during installation, thus drastically reducing installation time. During maintenance, these features are also useful for quickly detecting problems. Aspects of the invention allow faulty solar panels to be easily located, repaired or replaced. The bypass function of the present invention increases reliability when repair or replacement is not feasible.

In one aspect, the invention relates to a solar cell array combining battery power. Each inverter can be attached to a single solar cell or to multiple cells in series, parallel or both, for example, a parallel connection of strings of series cells. In one embodiment, each inverter is attached to one photovoltaic string panel. However, aspects of the present invention, while applicable in the field of solar power generation, can also be used in any distribution network using DC power. For example, these aspects can be used in batteries with multiple cells or in hybrid vehicles with multiple on-board fuel cells. The DC power source can be a solar cell, a solar panel, a fuel cell, a storage battery, and the like. Additionally, although the following discussion refers to combining power from an array of DC power sources into an AC voltage source, aspects of the invention may also be used to combine power from DC power sources into another DC voltage.

Figure 3 shows a power distribution collection arrangement 30 in an embodiment of the invention. Configuration 30 allows for connecting multiple power sources (eg, solar panels 301a-301d) to a single power source. In one aspect of the invention, a series string of all solar panels may be connected to the inverter 304 . In another aspect of the invention, several series strings of solar panels may be connected to a single inverter 304 . Inverter 304 may be replaced by other elements, such as a charge regulator for charging the battery pack.

In configuration 30, each solar panel 301a-301d is connected to a separate power converter circuit 305a-305d. A solar panel and its associated power converter circuitry make up a module, such as module 320 . Each inverter 305a-305d adapts in an optimal manner to the power characteristics of the connected solar panels 301a-301d and efficiently transfers power from the inverter input to the inverter output. The converters 305a-305d may be buck converters, boost converters, buck/boost converters, flyback converters, or forward converters, among others. Converters 305a-305d may also include many constituent converters, eg, a series connection of buck and boost converters.

Each inverter 305a - 305d includes a control loop that, instead of outputting current or voltage from the inverter, receives a feedback signal from the input of the inverter from the solar panel 301 . An example of such a control loop is a maximum power point tracking (MPPT) loop. The MPPT loop in the converter locks the input voltage and current from each solar panel 301a-301d to the optimum power point.

A conventional DC/DC converter has a large input voltage range at the input and a predetermined and constant output voltage. In a traditional DC/DC voltage converter, a controller within the converter monitors the current or voltage at the input and the voltage at the output. A controller determines an appropriate pulse width modulation (PWM) duty cycle and increases the duty cycle if the output voltage drops, thereby fixing the output voltage to a predetermined value. Thus, conventional converters include a feedback loop that is closed on the output voltage and uses the output voltage to further regulate and trim the output voltage of the converter. As the output voltage is changed, the current drawn from the input is also changed.

In inverters 305a-305d, in an aspect of the invention, a controller within inverter 405 monitors the voltage and current at the inverter input and determines the PWM such that maximum power is drawn from the attached panels 301a-301d. The controller of converter 405 dynamically tracks the maximum power point at the input of the converter. In aspects of the present invention, the feedback loop is closed on the input power to track the maximum input power, instead of closing the feedback loop on the output voltage as in conventional DC/DC voltage converters.

Because there is a separate MPPT circuit in each inverter 305a-305d, for each solar panel 301a-301d, each string 303 in the embodiment shown in FIG. The circuit of Figure 3 performs MPPT continuously on the output of each solar panel 301a-301d in response to changes in temperature, solar radiation, shading or other performance factors affecting that particular solar panel 301a-301d. Thus, the MPPT circuitry within inverters 305a-305d harvests the maximum power possible from each panel 301a-301d and delivers this power as an output, independent of parameters affecting other solar panels.

Thus, the aspect of the invention shown in FIG. 3 continuously tracks and maintains the input current and input voltage of each converter at the maximum power point of the DC power supply supplying the input current and voltage to the converters. The maximum power of the DC power supply is the input and output of the converter. The converter output power may be a different current and voltage than the converter input current and voltage. The output current and voltage of the converter respond to the requirements of the series part of the circuit.

In one aspect of the invention, the outputs of the converters 305a-305d are connected in series into a single DC output which forms the input to a load or power supply (in this example, inverter 304). Inverter 304 converts the series DC output of the converters to AC power. The load (in this example, the inverter 304) regulates the voltage at the input of the load. That is, in this example, a separate control loop 320 maintains the input voltage at a set point, ie, 400 volts. Thus, the input current to the inverter is controlled by the real power, which is the current flowing through all the DC sources in series. On the other hand, although the output of the DC-DC converter must be the current input of the inverter, the current and voltage inputs of the converter are independently controlled using MPPT.

In the prior art, the load input voltage is allowed to vary with the effective power. For example, when the sun is shining in a solar installation, the voltage input to the inverter may even vary by as much as 1000 volts. Thus, as the amount of sunlight varies, the voltage varies, and the electrical components in the inverter (or other power supply or load) are subjected to varying voltages. This tends to degrade the performance of the component and eventually cause the component to fail. On the other hand, by fixing the input voltage or current of the load or power supply device (inverter here), the electrical components are always subjected to the same voltage or current, thus prolonging the service life. For example, load elements (eg, capacitors, switches, and coils of inverters) can be chosen such that the load elements operate at a fixed input voltage or current, ie, 60% of their rated value. This increases reliability and extends component life, which is critical to avoid loss of use in applications such as solar power systems.

Figures 4A and 4B illustrate the operation of the system of Figure 3 under different conditions in an aspect of the present invention. Exemplary configuration 40 is similar to configuration 30 of FIG. 3 . In the example shown, ten DC power supplies 401/1 to 401/10 are connected to ten power converters 405/1 to 405/10, respectively. The modules composed of DC power supplies and their corresponding converters are connected in series to form a string 403 . In one aspect of the invention, the series converter 405 is connected to the DC/AC converter 404 .

The DC power source can be a solar panel, and an example is discussed with a solar panel as an illustrative example. Each solar panel 401 may have a different power output due to manufacturing tolerances, shading, or other factors. As far as this example is concerned, FIG. 4A shows an ideal situation, where the DC/DC conversion efficiency is assumed to be 100%, and the battery panels 501 are assumed to be the same. In some aspects of the invention, the efficiency of the converter can be quite high, in the range of about 95%-99%. Therefore, it is reasonable to assume 100% efficiency for the sake of illustration. In addition, in the embodiments of the present invention, each DC-DC converter is regarded as a power converter, that is, the converter transfers all the power it receives at the input to the output with very little loss.

The power output of each solar panel 401 is maintained at the panel's maximum power point by a control loop within the respective power converter 405 . In the example shown in Figure 4A, all panels are exposed to sufficient sunlight and each solar panel 401 provides 200W of power. Thus, the MPPT loop will draw the current and voltage level to deliver the full 200W from the panel to its associated inverter. That is, the current and voltage controlled by the MPPT constitute the input current Im and the input voltage Vm of the converter. The output voltage is controlled by a constant voltage set at the inverter 404, as described below. The output current Iout is the total power (ie 200W) divided by the output voltage Vout.

As noted above, in accordance with a feature of the invention, the input voltage to the inverter 404 is controlled (in this example, held constant) via the control loop 420 to the inverter 404 . For the purposes of this example, assume that the input voltage is maintained at 400V (ideal for conversion to 220VAC). Since we assume ten power converters in series, each supplying 200W, we can see that the input current to the inverter 404 is 2000W/400V=5A. Thus, the current flowing through each inverter 401/1-401/10 must be 5A. This means that in this ideal example, each converter provides an output voltage of 200W/5A=40V. Now, assume that the MPPT of each panel (assuming perfectly matched panels) controls Vmpp=32V. This means that the input voltage of the inverter is 32V, and the input current is 200W/32V=6.25A.

We now turn to another example where the system is still kept in ideal mode (i.e., perfectly matched DC sources and full power is delivered to the inverter), but the ambient conditions are not ideal. For example, one DC power supply is overheated, malfunctioning, or as shown in the example of Fig. 4B, the ninth solar panel 401/9 is blocked from light and thus only produces 40W of power. Since we keep all other conditions as in the example of Fig. 4A, the other nine solar panels 401 are not shaded and still produce 200W of power. The power converter 405/9 includes MPPT to maintain the solar panel 501/9 operating at the maximum power point, which is now dropped due to shading.

The total active power of this string is now 9x200W+40W=1840W. Because the input of the inverter is still kept at 400V, the input current of the inverter is now 1840W/40V=4.6A. This means that the output of all power converters 405/1-405/10 in the string must be 4.6A. Therefore, for nine unblocked panels, the converter will output 200W/4.6A=43.5V. On the other hand, the inverter 405/9 attached to the blocked panel 401/9 will output 40W/4.6A=8.7V. Checking the calculation, adding nine converters for 43.5V and one converter for 8.7V gives the input to the inverter, ie (9x43.5V)+8.7V=400V.

As shown in Figure 4A, the output of the nine unblocked panels is still controlled by the MPPT and thus remains at 32V and 6.25A. On the other hand, since the ninth panel 401/9 is blocked from light, it is assumed that its MPPT drops to 28V. Therefore, the output current of the ninth battery panel is 40W/28V=1.43A. As shown in this example, all panels operate at maximum power point regardless of operating conditions. As shown in the example of Figure 4B, even if the output of one DC source drops significantly, the system fixes the input voltage of the inverter and individually controls the input of the converter to extract power from the DC source at the maximum power point, thereby maintaining relatively low voltage. High power output.

As expected, the zopo benefits shown in Figures 4A and 4B are enormous. For example, the output characteristics of series-connected DC power supplies such as solar panels do not have to match. Thus, series strings may use panels from different manufacturers or panels installed in different parts of the roof (ie in different spatial directions). Also, if several strings are connected in parallel, the strings do not have to match, instead each string can have a different panel or a different number of panels. This topology also reduces hot spot issues, thereby increasing reliability. That is, as shown in FIG. 4A , the output current of the battery panel 401 / 9 that is blocked from light is 1.43A, while the output current of the battery panel that is not blocked from light is 6.25A. When elements are connected in series, this current difference can force high currents to flow through the blocked panel, possibly causing the element to overheat and fail. However, in the topology of the invention, the input voltage is set individually, and the power extracted from each panel to its converter is individually set according to the maximum power point of the panel at each time, so the current of each panel is the same as that from the series converter The extracted current is irrelevant.

It is easy to realize that in a BIPV installation it is possible to install panels in different planes and orientations because the power is optimized for each panel individually. Thus, the problem of low power application in building integrated facilities is solved and more facilities are now profitable.

The system also easily addresses energy harvesting in low light conditions. Even a small amount of light is enough to run the converter 405, which then starts delivering power to the inverter. If there is a small amount of power, there will be low current, but high voltage enough for the inverter to run and indeed power to be harvested.

In an aspect of the invention, the inverter 404 includes a control loop 420 to maintain an optimum voltage at the input of the inverter 404 . In the example of FIG. 4B , the input voltage to the inverter 404 is maintained at 400V by the control loop 420 . Converter 405 is delivering essentially all of the real power from the solar panels to the input of inverter 404 . Therefore, the input current of the inverter 404 depends only on the power supplied by the solar panels and the setting of the regulation, ie the constant voltage at the input of the inverter.

The conventional inverter 104 shown in FIGS. 1 and 3A requires a very wide range of input voltages to accommodate varying conditions, such as variations in illuminance, temperature, and aging of the solar array. This is in contrast to the design of the inverter 404 in aspects of the invention. Inverter 404 does not require a wide range of input voltages, so the design is simpler and more reliable. Among these is the fact that there are no voltage spikes at the inverter input, so the components of the inverter are less electrically stressed and last longer, thereby achieving higher reliability.

When the inverter 404 is part of the circuit, the power from the panel is delivered to a load which may be connected to the inverter. In order for the inverter 404 to operate at the optimum input voltage, excess power generated by the solar array but not used by the load will be dissipated. Excess power can be disposed of by selling it to the utility company (if this option is an option). For off-grid solar arrays, excess power can be stored in batteries. Another option is to connect many neighboring houses together to form a microgrid and load balance the power between the houses. If the excess power provided by the solar array is not stored or sold, other mechanisms can be provided to dissipate the excess power.

The features and benefits described with respect to FIGS. 4A and 4B result at least in part from having the voltage provided at the inverter control input. Instead, a design in which the inverter controls the current at the input can be implemented. Figure 4C shows such a configuration. Figure 4C shows an embodiment of the present invention, in this case, the input current is controlled by an inverter. The power output of each solar panel 401 is maintained at the panel's maximum power point by a control loop within the respective power converter 405 . In the example shown in Figure 4C, all panels are exposed to sufficient sunlight and each solar panel 401 provides 200W of power. Thus, the MPPT loop will draw the current and voltage level to deliver the full 200W from the panel to its associated inverter. That is, the current and voltage controlled by the MPPT constitute the input current Im and the input voltage Vm of the converter. The output voltage is controlled by a constant current set at the inverter 404, as described below. The output voltage Vout is the total power (ie 200W) divided by the output current Iout.

As mentioned above, according to the features of the present invention, the input current of the inverter 404 is controlled by the inverter via the control loop 420 . For the purposes of this example, assume that the input current is maintained at 5A. Since we assume ten power converters in series, each supplying 200W, we can see that the input voltage to the inverter 404 is 2000W/5A=400V. Thus, the current flowing through each inverter 401/1-401/10 must be 5A. This means that in this ideal example, each converter provides an output voltage of 200W/5A=40V. Now, assume that the MPPT of each panel (assuming perfectly matched panels) controls Vmpp=32V. This means that the input voltage of the inverter is 32V, and the input current is 200W/32V=6.25A.

Thus, a similar advantage can be obtained by having the inverter control the current rather than the voltage. However, unlike existing technologies, changes in panel output do not cause changes in the current flow to the inverter, since the inverter itself controls this. Therefore, if the inverter is designed to hold the current or voltage constant, the current or voltage to the inverter will remain constant regardless of the panel operation.

Fig. 5 shows a power distribution collection system using a DC power supply in another aspect of the present invention. Figure 5 shows multiple strings 503 connected together in parallel. Each string is a series connection of multiple modules, and each module includes a DC power supply 501 connected to a converter 505 . The DC power source can be a solar panel. The parallel output of string 503 is again connected in parallel to shunt regulator 506 and load controller 504 . As with the embodiment of Figures 4A and 4B, the load controller 504 may be an inverter. A shunt regulator automatically maintains a constant voltage across the terminals. Shunt regulator 506 is configured to dissipate excess power in order to maintain the input voltage at the input of inverter 504 at a regulated level and prevent the inverter input voltage from increasing. The current flowing through the shunt regulator 506 supplements the current drawn by the inverter 504 to ensure that the input voltage of the inverter remains at a constant level, eg 400V.

By fixing the inverter input voltage, the input current of the inverter varies with the extracted real power. This battery is distributed between strings 503 of series converters. When each converter includes a control loop for maintaining the converter input voltage at the maximum power point of the associated DC source, the output power of the converter is determined. Converter power and converter output current together determine the converter output voltage. The converter output voltage is used by the power conversion circuitry in the converter to step up or down the converter input voltage to derive the converter output voltage from the input voltage determined by the MPPT.

Figure 6 shows an exemplary DC/DC converter 605 in an aspect of the invention. DC/DC converters are commonly used to step down or step up a varying or constant DC voltage input to a higher or lower constant voltage output, depending on the requirements of the circuit. However, in the embodiment of Figure 6, the DC-DC converter is used as a power converter, i.e. converts input power to output power, the input voltage varies with MPPT, and the output current is controlled by the constant input voltage of the inverter. That is, the input voltage and current can vary at any time, and the output voltage and current can also vary at any time, depending on the operating conditions of the DC power supply.

The converter 605 is connected to a corresponding DC power source 601 at input terminals 614 and 616 . The converted power of the DC power supply 601 is output to the circuit through the output terminals 610 and 612 . The remainder of the converter circuit is located between the input terminals 614, 616 and the output terminals 610, 612, including input and output capacitors 620, 640, backflow prevention diodes 622, 642, and power conversion circuitry (including the controller 606 and inductor 608) .

Inputs 616 and 614 are separated by capacitor 620 which acts as an open circuit to DC voltage. Outputs 610 and 612 are also separated by capacitor 640 which also serves as an open circuit terminal for the DC output voltage. These capacitors are DC blocking or AC coupling capacitors that will short out when faced with AC at the frequency for which the capacitor is selected. A capacitor 640 coupled between the outputs 610, 612 is also used as part of the power conversion circuit described below.

Diode 642 is coupled between outputs 610 and 612 and is polarized such that current cannot flow back from the positive lead of output 612 to converter 605. Diode 622 is coupled between positive output lead 612 through inductor 608 shorted to DC and negative input lead 614 polarized to prevent current from flowing back from output 612 to solar panel 601 .

The DC power source 601 can be a solar panel. There is a potential difference between the wires 614 and 616 due to the electron-hole pairs generated in the solar cells of the panel 601 . The inverter 605 continuously monitors the current and voltage supplied by the panels and uses a maximum power point tracking algorithm to maintain maximum power output at the maximum power point by drawing current from the solar panels 601 . Controller 606 includes MPPT circuitry or algorithms for tracking maximum power. Maximum Power Tracking and PWM are performed together to achieve the desired input voltage and current. The MPPT in the controller 606 can be a conventional MPPT, such as perturbation and observation (P&O), incremental conductance, and the like. However, it is obvious that MPPT is performed directly on the panel, ie at the input of the converter, not at the output of the converter. The generated power is then delivered to output terminals 610 and 612 . The outputs of multiple inverters 605 can be connected in series such that the positive lead 612 of one inverter 605 is connected to the negative lead 610 of the next inverter 605 .

In FIG. 6, the converter 605 shown is a buck plus boost converter. The term "buck-boost" as used here is a buck converter directly followed by a boost converter, as shown in Figure 6, which may also be referred to as a "cascaded buck-boost converter" in the literature. If you want to step down the voltage, the boost part is essentially a short circuit. If you want to step up the voltage, the step-down part is essentially a short circuit. The term "buck plus boost" differs from the buck-boost topology, which is a classic topology that can be used when you want to step up or down the voltage. The "buck/boost" topology is inherently less efficient than buck or boost. Also, for certain requirements, a buck-boost converter requires larger passive components than a buck-boost converter to operate. Therefore, the buck-boost topology of Figure 6 is more efficient than the buck-boost topology. However, the circuit of Figure 6 is constantly deciding whether to buck or boost. In some cases, both the buck and boost sections may operate when the desired output voltage is similar to the input voltage.

The controller 606 may include a pulse width modulator PWM or a digital pulse width modulator DPWM for use with buck and boost converter circuits. The controller 606 controls both the buck converter and the boost converter, and decides whether to buck or boost the voltage. In some cases, the buck and boost sections may be run together. That is, as described with respect to the embodiment of FIGS. 4A and 4B, the selection of input voltage and current is independent of the selection of output current and voltage. Additionally, the choice of input or output value may vary at any given moment, depending on the operation of the DC power supply. Thus, in the embodiment of FIG. 6, the converter is constructed such that at any given time, selected values of the input voltage and current can be shifted up or down depending on the output requirements.

In one embodiment, an integrated circuit (IC) 604 combining some of the functions of the converter 605 may be used. Optionally with IC 604, a single ASIC can withstand the extremely harsh temperatures found in outdoor solar installations. The ASIC 604 can be designed for a long mean time between failures (MTBF) of more than 25 years. However, a discrete solution using multiple integrated circuits can also be used in a similar manner. In the exemplary embodiment shown in FIG. 6 , the buck plus boost portion of converter 605 is implemented as IC 604 . When practically considered, the system can be partitioned in other ways. For example, in one aspect of the invention, IC 604 may include two integrated circuits: an analog integrated circuit that handles the high currents and voltages in the system and a simple low voltage digital integrated circuit that includes the control logic. Analog integrated circuits can be implemented using power field effect transistors, and power field effect transistors can be implemented using discrete components, FET drivers, A/Ds, and the like. A digital integrated circuit may constitute the controller 606 .

In the exemplary circuit shown, the buck converter includes an input capacitor 620 , transistors 628 and 630 , a diode 622 in parallel with transistor 628 , and an inductor 608 . Transistors 628, 630 have parasitic body diodes 624, 626, respectively. In the exemplary circuit shown, the boost converter includes an inductor 608 , transistors 648 and 650 , a diode 642 in parallel with transistor 650 , and an output capacitor 640 shared with the buck converter. Transistors 648, 650 have parasitic body diodes 644, 646, respectively.

As shown in Figure 1, adding electronic components in a series configuration can reduce the reliability of the system because if one electrical component fails, it can affect the entire system. Specifically, if one of the series elements fails creating an open circuit in the failed element, current stops flowing through the entire string, thereby causing the entire system to stop functioning. Aspects of the invention provide converter circuits in which electrical components of the circuit have one or more shunts associated therewith that can carry current if the electrical component fails. For example, each switching transistor in the buck or boost section of the converter has its own bypass. In the event of a switching transistor failure, this element of the circuit is bypassed. Likewise, when an inductor fails, current bypasses the failed inductor through the parasitic diodes of the transistors used in the boost converter.

Figure 7 shows a power converter in an aspect of the invention. Among them, FIG. 7 emphasizes the monitoring function of the DC/DC converter 705 in the embodiment of the present invention. Also shown is a DC voltage source 701 . Simplified buck and boost converter circuit portions of converter 705 are shown. The portion shown includes switching transistors 728 , 730 , 748 and 750 and common inductor 708 . Each switching transistor is controlled by a power conversion controller 706 .

The power conversion controller 706 includes a pulse width modulation (PWM) circuit 733 and a digital control machine 730 (including a protection section 737 ). The power conversion controller 706 is connected to a microcontroller 790 (including an MPPT module 719 ), and optionally includes a communication module 709 , a monitoring and recording module 711 and a protection module 735 .

The current sensor 703 may be coupled between the DC power source 701 and the converter 705 , and the output of the current sensor 703 may be provided to a digital control machine 730 via an associated analog-to-digital converter 723 . The voltage sensor 704 may be coupled between the DC power source 701 and the converter 705 , and the output of the voltage sensor 704 may be provided to a digital control machine 730 via an associated analog-to-digital converter 723 . The current sensor 703 and the voltage sensor 704 are used to monitor the current and voltage output by the DC power supply (eg, the solar panel 701 ). The measured current and voltage are provided to the digital control engine 730 and used to maintain the converter input power at the maximum power point.

PWM circuit 733 controls the switching transistors of the buck and boost sections of the converter circuit. The PWM circuit may be a digital pulse width modulation (DPWM) circuit. The output of the converter 705 from the inductor 708 and the switching transistor 750 is supplied to the digital control machine 730 via the analog-to-digital converters 741 , 742 to control the PWM circuit 733 .

Random access memory (RAM) module 715 and non-volatile random access memory (NVRAM) module 713 may be located outside microcontroller 790 but connected to microcontroller 790 . A temperature sensor 779 and one or more external sensor interfaces 707 may be connected to a microcontroller 790 . A temperature sensor 779 may be used to measure the temperature of the DC power supply 701 . The physical interface 717 is connectable to the microcontroller 790 and is used to translate data from the microcontroller into standard communication protocols and physical layers. An internal power supply 739 may be included in the converter 705 .

In various aspects of the invention, current sensor 703 may be implemented using various techniques for measuring current. In one aspect of the invention, the current measurement module 703 is implemented using very low value resistors. The voltage across the resistor is proportional to the current flowing through the resistor. In another aspect of the present invention, the current measurement module 703 is implemented using a current probe, which uses the Hall effect to measure the current flowing through the conductor without adding a series resistor. After converting the current to voltage, the data can be passed through a low-pass filter before being digitized. An analog-to-digital converter associated with the current sensor 703 is shown in FIG. 7 as an A/D converter 723 . By choosing the proper resolution and sampling speed for the ADC, aliasing effects in the generated digital data can be avoided. If the current sensing technique does not require series connection, then the current sensor 703 can be connected in parallel to the DC power supply 701 .

In one aspect of the invention, the voltage sensor 704 employs a simple shunt voltage measurement technique in order to measure the voltage output of the solar panel. The analog voltage is passed through a low-pass filter to reduce distortion. The data is then digitized using an analog-to-digital converter. The analog-to-digital converter associated with voltage sensor 704 is shown as A/D converter 724 in FIG. 7 . The A/D converter 724 has sufficient resolution to generate a properly sampled digital signal from an analog voltage measured at a DC power source 701, which may be a solar panel.

Current and voltage data collected to track the maximum power point on the converter input signal can also be used for monitoring purposes. An analog-to-digital converter with sufficient resolution can correctly estimate the voltage and current values of the panel. However, to estimate the state of the panel, a lower sampling rate is sufficient. A low-pass filter allows a low sampling rate sufficient for panel state estimation. Current and voltage data can be provided to the monitoring and recording module 711 for analysis.

A temperature sensor 779 allows the system to utilize temperature data during analysis. Temperature is an indication of certain types of malfunctions and problems. Also, where the power source is a solar panel, the temperature of the panel is a factor in the production of power output.

One or more optional external sensor interfaces 707 can connect different external sensors to the transducer 705 . External sensors are optional to enhance the analysis of the status of the solar panel 701, or a string or matrix of connected solar panels. Examples of external sensors are ambient temperature sensors, solar radiation sensors, and sensors adjacent to the panels. External sensors are integrated into the transducer 705 rather than mounted externally.

In one aspect of the invention, the information obtained from the current and voltage sensors 703, 704 and optional temperature and external sensors 705, 707 can be transmitted to a central analysis station for monitoring, control and analysis using the communication interface 709. The central analysis station is not shown in the figure. Communication interface 709 connects a microcontroller 790 to the communication bus. The communication interface can be implemented in several ways. In one aspect of the invention, the communication interface is implemented using an off-the-shelf communication bus, such as Ethernet or RS422. Other methods like wireless communication, or power line communication implemented on the power lines connecting the panels may also be used. If two-way communication is used, the central analysis station can request the data collected by the microcontroller 790 . As an option or in addition, the information obtained from the sensors 703, 704, 705, 707 is recorded locally using a monitoring and recording module 711 in local memory, such as RAM 715 or NVRAM 713.

By analysis of the information obtained in the sensors 703, 704, 705, 707, it is possible to detect and determine the location of various faults related to power loss in the solar matrix. Smart analytics can also be used to suggest corrections such as cleaning or replacing specific parts of the solar matrix. The analysis of the sensor information also detects power losses caused by environmental conditions or installation errors, avoiding costly and laborious testing of solar matrices.

Thus, in one aspect of the invention, the microcontroller 790 can simultaneously maintain the maximum power point of the input power delivered to the inverter 705 from the additional DC power source or solar panel 701 and manage slave sensor The process of gathering information in 703, 704, 705, 707. The collected information can be stored in local memory 713, 715 and transmitted to an external central analysis station. In one aspect of the invention, microcontroller 790 employs pre-defined parameters stored in NVRAM 713 for ease of operation. Information stored in NVRAM 713 may include transducer 705 information such as serial number, type of communication bus used, status update rate and ID of the central analysis station. This message can be added to the parameters collected by the sensor before being sent.

Inverter 705 may be installed during installation of a solar matrix or retrofitting an existing installation. In both cases, the converter 705 can be connected to a panel junction box or to the cable connecting the panel 701 . Each inverter 705 is provided with connectors and cabling to facilitate installation and connection to solar panels 701 and panel cables.

In one aspect of the invention, the physical interface 717 is used to convert to a standard communication protocol and physical layer; thus, during installation and maintenance, the converter 705 can be connected to one of the different data terminals, Such as a computer or PDA. At this point, the analysis can be implemented as software that can run on a standard computer, embedded platform, or proprietary device.

The installation process of the inverters 705 includes attaching each inverter 705 to the solar panel 701 . More than one sensor 703, 704, 705, 707 may be used to ensure that the solar panel 701 and inverter 705 are properly coupled together. Parameters such as serial number, physical location and matrix connection layout may be stored in NVRAM 713 during installation. These parameters can be used by analysis software to detect future problems in the solar panel 701 and matrix.

One of the issues facing photovoltaic solar panel matrix installers when the DC power source 701 is a solar panel is safety. When there is sunlight during the day, the solar panels 701 are connected in series. Therefore, in the final stages of installation, when several solar panels 701 are connected in series, the voltage across the string of panels may reach dangerous levels. In home-installed panels, the voltage is often as high as 600V. Therefore, the installer faces the risk of electric shock. The inverter 705 connected to the battery panel 701 can take advantage of built-in functions to prevent such hazards. For example, converter 705 may include hardware circuitry or software modules that may limit the output voltage to a safe level until a predetermined minimum load is detected. Only after detecting this predetermined load, the microcontroller 790 will boost the output voltage of the converter 705 .

Another way to provide a safety mechanism is to utilize communication between the converter 705 and the panel string or matrix related inverters. For example, this means of communication may be a power line communication device that provides simultaneous information exchange before providing high or potentially hazardous levels. Therefore, the converter 705 waits for the inverter analog or digital release signal in the correlation matrix before transferring power to the inverter.

The above monitoring, control and analysis methods of DC power supply 701 can be implemented on solar panels or strings or matrices of solar panels, or on other power sources like batteries and fuel cells.

Fig. 8 shows an arrangement of solar panels according to the prior art. In FIG. 8 , a solar panel 800 consists of solar cells 805 divided into several series strings 810 of cells. The battery strings 810 are connected together in series. For each battery string 810, a bypass diode 820 is provided so that when the power output of a battery string drops, the battery string can be bypassed through the corresponding diode 820 instead of allowing the battery to enter the negative voltage region, which would cause The power dissipated across the battery could even cause a burn. However, when current flows through diodes, they dissipate energy. For example, if a current of 5A flows through an ordinary diode with a turn-on voltage of 0.7 volts, the power loss is 3.5W. In practice, this loss can easily rise to 10W.

Figure 9 presents an array diagram according to a specific device invented to reduce power loss in a solar cell string. In FIG. 9 , a solar panel 900 is composed of solar cells 905 divided into several series strings 910 of cells. The battery strings 910 are connected together in series. For each battery string 910, a bypass diode 920 is provided so that when the power output of a battery string drops, the battery string can be bypassed through the corresponding diode 920. Furthermore, a switching device 925 is connected in the bypass circuit in order to bypass the corresponding diodes, such as FETs or IGBTs (Insulated Gate Bipolar Transistors). Once current is sensed flowing through one diode 920 (or once the sensed voltage across the battery string 910 is negative), its corresponding switching device 925 is triggered. This directs the current through the switching device, which drastically reduces energy losses. For example, sensing can be accomplished by sensing the voltage across a battery string or the current across a diode.

Figure 10 shows an alternative arrangement according to the specific device invented to reduce the power loss in the solar cell string. In FIG. 10 , a solar panel 1000 consists of solar cells 1005 which are divided into several series strings 1010 of cells. The battery strings 1010 are connected together in parallel. For each battery string 1010, a bypass switch device 1025 is provided so that when the power output of a battery string drops, the battery string can be bypassed by a corresponding switch device 1025, such as a FET or IGBT. Once the battery string 1010 is sensed to be in reverse bias (whether due to poor light or a fault), the corresponding switching device 1025 is turned on so that current can flow through the respective switching device 1025 . For example, sensing can be achieved by sensing the voltage or current of the battery string.

Figure 11 shows an arrangement diagram according to the specific device invented by the bypass solar cell string. That is, FIG. 11 shows how a converter, such as the converter in FIG. 6 , can be used to trigger the bypassing of solar cell strings and/or diodes coupled across the solar cell strings. In FIG. 11 , a solar panel 1100 is composed of solar cells 1105 divided into several series strings 1110 of cells. The battery strings 1110 are connected together in parallel. For each battery string 1110, a bypass diode 1120 is provided so that when the power output of a battery string drops, the battery string can be bypassed through the corresponding diode 1120. However, as explained in Figure 10, the diodes can be eliminated. Additionally, a switching device 1125 is connected to the bypass circuit, such as a FET or IGBT, to bypass the corresponding battery string 1110 and/or diode 1120 . Once the battery string 1010 is sensed to be in reverse bias, its corresponding switching device 1125 is triggered by the controller 906 . This allows current to be directed through the switching device 1125 to substantially reduce energy loss. Sensing can be achieved, for example, by sensing the voltage across a battery string or the current across a diode, as explained for elements 703 and 704 in FIG. 7 .

The present invention has been described with respect to particular examples, which are intended in all respects to be illustrative rather than restrictive. Those familiar with the art will appreciate that many different combinations of hardware, software, and firmware would be suitable for practicing the present invention. Moreover, other methods of carrying out the invention will obviously cause those skilled in the art to consider the specification and practice of the invention disclosed herein. It is intended that the specifications and examples be considered as examples only, with the true scope and spirit of the invention being indicated by the following claims and their equivalents.

Claims (37)

1. A distributed power harvesting system comprising: Numerous DC power supplies; Numerous transformers, each of which includes: Input terminals connected to corresponding DC power sources; output terminals connected in series with other converters, thereby forming a series string; an MPPT section, which sets the voltage and current of the input terminals of the converter to the maximum power point of the corresponding DC power supply; and a power conversion section for converting electrical energy received at the input terminal into output power at the output terminal; and an energy supplier connected in series, the energy supplier including a control section responsible for maintaining the input voltage of the energy supplier at a predetermined value. 2. The distributed power harvesting system according to claim 1, wherein the energy supplier comprises a DC/AC inverter. 3. The distributed power harvesting system of claim 1, wherein the energy supplier comprises a battery charger. 4. The distributed power harvesting system according to claim 1, wherein the power conversion part comprises: a buck converter; a boost converter; and a controller that can selectively trigger a buck converter or a boost converter in response to changes in current or voltage of the MPPT section and output terminals, wherein the voltage and current of the input terminals are selected in relation to the current and voltage of the output terminals irrelevant. 5. The distributed power harvesting system according to claim 4, wherein the inductor is shared by the buck converter and the boost converter, and the controller includes a pulse width modulation part. 6. The distributed power harvesting system according to claim 1, wherein the control part comprises a shunt voltage regulator connected in parallel with the input terminal of the energy supplier, responsible for regulating the input voltage of the input terminal of the energy supplier to a predetermined constant value . 7. The distributed power harvesting system of claim 1, further comprising more than one additional series-connected battery string connected to the energy supplier. 8. The distributed power harvesting system according to claim 1, further comprising: a plurality of current sensors; and Multiple voltage sensors; Each current sensor and each voltage sensor therein are connected between the corresponding converter and the DC power supply, and provide current information and voltage information to the MPPT part. 9. The distributed power harvesting system of claim 1, wherein each of the plurality of DC power sources comprises a solar panel or a building incorporating a solar panel. 10. The distributed power harvesting system of claim 1, wherein at least one power source of the plurality of DC power sources includes a fuel cell. 11. The distributed power harvesting system of claim 1, wherein at least one of the plurality of DC power sources comprises a battery. 12. The distributed power harvesting system according to claim 1, wherein each converter in the plurality of converters further includes a safety module, which can limit the output power of the converter to a preset safe value until a predetermined event until it happens. 13. The distributed power harvesting system according to claim 12, wherein the predetermined event includes a load from the energy supplier exceeding a preset threshold is applied to the converter, or a release signal from the energy supplier is detected. 14. The distributed power harvesting system of claim 1, wherein each converter further comprises a plurality of switching devices, each of said plurality of switching devices constituting a bypass for the respective DC power source. 15. The distributed power harvesting system according to claim 9, wherein the solar panel comprises a plurality of battery strings, each battery string comprises solar cells connected in series, and a switching device is connected to bypass the solar cells connected in series. 16. The distributed power harvesting system of claim 15, wherein the switching means comprises a transistor. 17. The distributed power harvesting system according to claim 1, wherein each converter further includes a monitoring module that monitors and transmits state-related data, and the state-related data includes at least one of the following data: the input current of the converter , the input voltage of the converter, the temperature of the power supply, the input power of the converter and the effective illuminance. 18. A method of obtaining power from a distributed power harvesting system having a plurality of DC power sources and a plurality of DC power converters, the method comprising: Connect each DC power supply to its own DC power converter; connecting output terminals of the power converters in series to form at least one series string; connecting said at least one series string to a power output device; Fixing an input voltage of the power output device at a predetermined constant value, whereby the current forced to flow through the series string varies according to the power of the supplied DC power supply; and Individually control the power output of each DC power supply by tracking the maximum power point of the DC power supply, and individually vary the input voltage and input current of each corresponding converter by setting the input voltage and input current to draw the maximum power from each DC power supply . 19. The method according to claim 18, wherein the process of connecting the series string to the power output device comprises connecting the series string to the input terminal of the DC/AC inverter and fixing the input voltage of the input terminal of the DC/AC inverter the process of. 20. The method of claim 18, further comprising converting the input power of each converter individually to output power, wherein the input power includes input voltage and input current, and the output power includes output voltage and output current, wherein, The output current is dictated by the current flowing through the series string, and the output voltage varies based on the input power. 21. The method of claim 19, further comprising individually converting the input power of each converter to an output power, wherein the input power includes an input voltage and an input current, and the output power includes an output voltage and an output current, wherein, The output current is dictated by the current flowing through the series string, and the output voltage varies based on the input power. 22. The method of claim 18, further comprising individually monitoring the load on each converter from the power output device and limiting the output of each converter to a preset safe level until the load reaches up to the default value. 23. The method of claim 18, further comprising monitoring the power output of the at least one power source and the DC power converter, and directing power from the power source when the power output of the at least one power source and the DC power converter exhibits predetermined characteristics. current to the bypass loop. 24. The method according to claim 18, further comprising operating each power converter individually to monitor and report power-related data; the power-related data includes at least one of the following data: input current of the converter, Input voltage, temperature of the power supply, input power of the converter and effective illuminance. 25. The solar power supply device includes: DC/AC inverters, including means for maintaining the inverter input voltage at a predetermined constant value; A plurality of series strings in parallel with the input of the DC/AC inverter, each series string comprising: Multiple solar panels; Complex transformers, each transformer consisting of: Input terminals for connection with corresponding solar panels; output terminals connected in series with other converters, thereby forming a series string; The MPPT section sets the voltage and current at the input terminals of the converter according to the maximum power point of the corresponding solar panel; and, A power conversion section for converting electrical energy received at the input terminal into output power at the output terminal. 26. The solar power supply device according to claim 25, wherein the power conversion part converts the power received by the input terminal into output power, and the current corresponding to the output power is actually equal to the total power provided by the plurality of solar panels in the series string divided by the inverse A predetermined constant value of the input voltage of the inverter. 27. The solar power supply device according to claim 25, wherein the power conversion part includes a power conversion controller, which is responsible for controlling the pulse width modulation of the power conversion part, so that the current corresponding to the output power is actually equal to the plurality of solar panels in the series string The total power provided is divided by a predetermined constant value of the input voltage of the inverter. 28. The solar power device of claim 25, wherein each power conversion section comprises: a buck converter; a boost converter; A digital controller that controls the pulse width modulator to selectively operate a buck converter or a boost converter in response to changes in current or voltage at the MPPT section and output terminals. 29. The solar power device of claim 25, wherein each series string further comprises: A plurality of current sensors, each sensor measures the output current of one solar panel and sends the measured current signal to the corresponding digital controller; and A plurality of voltage sensors, each sensor measures the output voltage of one solar panel and sends the measured voltage signal to the corresponding digital controller; Each of these digital controllers regulates the generated current and voltage for maximum available power. 30. The solar energy power supply device according to claim 25 further comprising a safety module, as long as no load from the DC/AC inverter above a preset threshold value is applied to the converter, the output voltage of the converter is limited to preset safe level. 31. The solar power supply device according to claim 25, wherein each solar cell panel includes a plurality of battery strings, each battery string includes solar cells connected in series, and a switching device is connected to bypass the solar cells connected in series. 32. A solar power arrangement according to claim 31, wherein the switching means comprises a transistor. 33. The solar power supply device according to claim 25, wherein each converter further comprises a monitoring module to monitor and send power-related data; the power-related data includes at least one of the following data: input current of the converter, conversion The input voltage of the device, the temperature of the plurality of solar panels, the spatial direction of the plurality of solar panels and the effective illuminance. 34. A method of increasing stability of components within a central load in a distributed power system having a plurality of DC power sources connected to the central load, the method comprising: connecting each of the plurality of DC power sources to a corresponding converter of the plurality of converters; connecting the output terminals of all converters in series to form a series string; Connect the series string to the central load; Individually control the power output of each DC power source by tracking the maximum power point of the DC power source, individually vary the input voltage and current of each corresponding converter by setting the input voltage and current so as to absorb the maximum power from each DC power source; maintain the input voltage to the central load at a fixed predetermined voltage which is a safe operating voltage for the internal components of the load; and Depending on the power drawn from the DC source, the value of the current input to the central load is varied. 35. The method of claim 34, wherein the central load comprises a DC/AC inverter. 36. The method of claim 35, wherein the step of connecting the series string to a central load includes connecting the series string to an input of a DC/AC inverter. 37. The method of claim 36, further comprising operating each inverter to boost the voltage obtained by the corresponding solar panel whenever the corresponding solar panel begins to output electrical power.